DSJ,
My mother was also found to have high TSH a few years ago but hers is the type hypothyroidism that older women get commonly with age however, your mother's could be a different type.
I have Hashimoto's Hypothyroidism (Autoimmune Type) and this is usually hereditary but strangly enough, my mom's is not the autoimmune type, just low-thyroid, for which she takes Synthroid (synthetic hormone replacement).
Christine's advice would be your best thing at this point and I hope they will get to the bottom of it for you soon!
That is a TSH on the high side, which means she is hypothyroid. Have you discussed your concerns with her doctor? Have they suggested any thyroid medicine? Your moms age and the fact she just had major surgery, I am sure is playing a part in the fatigue, along with the elevated thyroid levels. If you have not talked to her doctor about this, get on the phone and do so. Also request a copy of the labs that have been done on her. Is this the first she has been diagnosed with a high TSH? Did they check it before the surgery, if so what were those numbers like? this is the reason to request copies. So you know where she stood before and after surgery.